The present invention relates to a quickly released and fastened adjustment mechanism, especially to a quickly released and fastened adjustment mechanism that is fastened firmly while not in use and is released rapidly during adjustment. The quickly released and fastened adjustment mechanism including a gasket, a first ratchet, a second ratchet, a T-shaped sleeve and a fastener is installed between a sliding member and a fixing member. The adjustment mechanism is quickly released and moved for adjustment of the sliding member and then is fastened again by reverse operation.
An adjustment member is usually disposed between a sliding member and a fixing member. Take a height adjustment mechanism for armrests as an example. Refer to FIG. 1 (only a part of components related to prior arts are used to explain), the sliding member 2 is a horizontal support 205 for an armrest 204 of a chair while the fixing member 3 is a seat 301 of the chair. The horizontal support 205 for the armrest 204 is arranged at a bottom surface 302 of the seat 301 of the chair and an adjustment mechanism is set between the horizontal support 205 for the armrest 204 and the seat 301 of the chair. Thus the armrest 204 is able to be adjusted horizontally relative to the seat 301 after the adjustment mechanism being released (as the double-headed arrow A in figure one indicates). Then the adjustment mechanism has been secured tightly for positioning the armrest 204.
The adjustment mechanism mentioned above mainly includes a first ratchet, a second ratchet and a fastener (such as a screw). A first surface of the first ratchet is directly attached to a bottom surface 202 of a long step-like hole 201 on the horizontal support 205 of the armrest 204 while the second surface of the first ratchet is disposed with annular teeth. A first surface of the second ratchet is arranged with annular teeth corresponding to and engaged with the annular teeth of the first ratchet. The fastener is passed through a center hole of the second ratchet and a center hole of the first ratchet in turn to be secured and fixed on the bottom surface 302 of the seat 301 of the chair. However, the above adjustment mechanism has the following shortcomings while in use. During the assembly, the tightness of the fastener is difficult to control when the fastener is passed through the second ratchet and the first ratchet in to be secured on the bottom surface 302 of the seat 301. Once the fastener is too tight, users (especially women) is unable to easily operate the second ratchet to rotate relative to the first ratchet for changing the engagement state of the two annular teeth between the first and the second ratchets. If the fastener is loose, the horizontal support 205 of the armrest 204 is unable to be fastened on the bottom surface of the seat 301 stably no matter before or after the adjustment. Thus the armrest 204 is unstable or easy to get loose while in use. This significantly affects the use of the armrest 204, reliability and consumers' desire. This has negative effects on the installation of the armrest, mass production and market competitiveness.